I'd buy copper wiring with one thick strand in there (so not lots of thin strands), but not sure which size, thickness. For connecting wires together (inside the distributor boxes) that thing we call "chocolate" (pic #5 and 6) is a must. Old places usually have aluminium wires, and twisting together aluminium and copper wires will result in relatively quick oxidation, then sparks and maybe fires... So use chocolate. If you connect copper wires, use chocolate because it's just makes maintenance easier, and won't look like a patchwork.
The wiring should be code colored (pic #7). Black for Line, blue for 0, green-yellow for Ground. There are some alternative colorings, using red or brown, but I know these three and that's enough.
Also quite a few types of chocolates out there (pic #8).